In '65 the regular Chevelle models were:
About halfway through the model year Chevy decided to offer a special limited edition car to introduce the new big block to the Chevelle line (with a new SS396 model to come in model year 1966).
The Z16 package was an option (an RPO) although it could not be ordered by any dealer or customer. Chevy intended to make 201 cars and send them out to the more productive and visible dealerships (there were far more than 201 dealerships across the country) and to give a few away to celebrities to get some visibility.
The Z16 option was based ONLY on a Malibu SS V8 model. The Z16 package consisted of the following unique parts/treatments which differed from a standard Malibu SS:
-unique trim treatment on the rear of the car, 300-style tail light lenses, Malibu SS emblems moved to the front fenders, 396 Turbo Jet emblems on the front fenders, Malibu SS 396 badge on the trunk.
-Full size Chevy drum brakes were modified and installed on the Chevelle chassis, the Z16 used unique front spindles
-A narrowed full size Chevy 12-bolt rear axle fitted with Chevelle suspension brackets, all were installed WITHOUT positraction and included a rear sway bar and 3.31 gears
-Full size Chevy power steering gear box adapted to fit the Chevelle chassis.
-A convertible (boxed) frame
-A larger front sway bar
-Premium gold line bias ply 7.75x14 Firestone tires
-A 160mph speedometer
-A 5600 RPM redline tach (same as the L79 tach)
-A dashtop clock (optional on all other Chevelles)
-An AM/FM stereo multiplex sound system with additional speakers (an AM/FM radio was available on all other Chevelles, but not a STEREO, the stereo was unique to the Z16 this year)
-mag wheel hub caps (optional on other Chevelles)
-14x6 riveted Kelsey-Hayes wheels with a relief groove machined in to clear the larger brake drums
-A large flat dual snorkle air cleaner with a diecast 396/flags emblem (no cheap sticker here!)
-Remote control driver's side outside rear view mirror
-Comfort and convenience group (optional on all other Chevelles, included two-speed wipers and a day/night inside mirror)
-And of course a 375hp/396, the engine had hydraulic lifters and other than the hydraulic cam and exhaust manifolds, the engine was almost the same as the 425hp/396 installed in the Corvette in 1965
-The cars all got the same M20 4-speed available in any other V8 Chevelle that year
They came only in Regal Red, Tuxedo Black and Crocus Yellow. Many had vinyl tops (which were pretty rare in 1965). All other equipment unless replaced by Z16 items was basic Malibu SS stuff (console, bucket seats, grill treatment, remaining trim, etc.)
There are also many other small unique items required to fit the 396 in the Chevelle chassis and these along with the many unique items metioned above make a Z16 almost impossible to correctly clone without spending Z16-like money to get there!
The "option" cost over $1600 in 1965 dollars and practically doubled the cost of the car compared to a basic Malibu SS V8 car.
By the way, I've posted this info many, many times, a search of this site could answer these questions too.